An Iranian technician called Jalal-a-Din Taheri, who had been working at the nuclear reactor at Bushehr, managed to defect to Europe, where he disclosed the Ayatollahs’ plans for producing nuclear bombs.

Taheri was acclaimed a hero throughout the world. A number of organizations nominated him for the Nobel Peace Price. President Bush praised his courage. Ariel Sharon invited him to come and live in Israel, even calling him one of the Righteous of the Nations. The Ayatollahs denounced him as a traitor, infidel, Crusader and Zionist.

This is, of course, an entirely fictitious story. But it corresponds exactly to the story of Mordechai Vanunu, who is considered by almost all Israelis as a despicable traitor – proving once again that treason, like pornography, is a matter of geography.

This week I used my privilege as a former Member of the Knesset to attend a session of the Knesset Committee for "the Constitution, Law and Justice", in which the Vanunu affair was discussed. In the course of the session, Knesset members cursed each other in the language of fishmongers (by which I mean no offence to fishmongers). Two Likud members, Ronie Bar-On (who once served for several hours as Attorney General before being ignominiously removed) and Yehiel Hazan shouted that Vanunu had no human rights, since he was not a human being. It should be mentioned in all fairness that the chairman of the committee, Michael Eytan, also a Likud member, strongly condemned these utterances.

Vanunu, who in 1986 disclosed to a British newspaper some of Israel’s nuclear secrets, was kidnapped soon after by the Mossad, smuggled back to Israel and put on trial. He served his sentence: 18 years in prison. For most of the time he was held in total isolation. (He told me that, in order to keep his sanity, he would read the New Testament in English out loud, over and over again, and in this way improved his command of this language, which he now insists on using instead of Hebrew.)

On his release, he was placed under severe restrictions: he is forbidden to go abroad, forbidden to move inside the country without prior notification of the authorities, forbidden to speak with foreigners, forbidden to give interviews. The Supreme Court has upheld these constraints. Vanunu has violated most of them, and some weeks ago he was indicted for these violations.

The restrictions were initially imposed for one year, which came to an end this week. The Knesset committee was about to discuss the possibility of their being extended, but a few hours before the session, the Minister of the Interior, Ophir Pines (Labor Party) signed an order extending for another year the prohibition of leaving the country, and the Army Commander of the Home Front signed an order to extend the other constraints (under Emergency Regulations).

At the committee meeting, the representative of the Attorney General set out the government arguments for this extension: (a) Vanunu still "holds in his head" dangerous secrets, (b) He has a "phenomenal" memory, (c) If given the opportunity, he will disclose these secrets abroad.

What is the evidence to support this?

(a) In one of the letters he wrote in prison, Vanunu told his correspondent abroad that he was in possession of many more secrets, which he had not yet disclosed. He announced his intention of revealing these secrets at the first opportunity.

(b) Two years before his release – that is to say, 16 years after his work in the nuclear installation – he drew in his cell, purely from memory, detailed and amazingly exact blueprints of the production process. These drawings were found among the more than a thousand documents seized in his cell.

These facts are more than strange. An inmate who sends letters from prison knows, of course, that they are censored. Vanunu was bound to know that not only the prison authorities, but the intelligence services, too, would read them. When he made the blueprints, he certainly knew they would be seized.

All this indicates that he intended to provoke his tormentors and show them that he was not broken. It is difficult to take the documents seriously, as the Supreme Court did, eight months ago, when it confirmed the restrictions. A person who intends to disclose dreadful secrets does not announce this in advance to the authorities, and does not prepare blueprints for his persecutors.

Concerning the matter itself:

(a) Does he "hold in his head" secrets that he has not disclosed in the past?

Unlikely.

First of all, Vanunu’s knowledge concerns processes as they were 18 years ago. Can such knowledge be useful today? Hard to believe. As Knesset Member Zehava Galon (Yahad) remarked at the session: "It is terrifying to imagine that nothing has changed in Israel’s nuclear techniques for 19 years!"

Secondly, before the British paper published his disclosures, Vanunu was cross-questioned for two whole days by one of the world’s leading nuclear scientists. It is hard to believe that after that he still had any undisclosed secrets left.

Thirdly, it borders on paranoia to think that he was so sophisticated as to decide, 18 years ago, to "hold in his head" secrets in order to publish them 20 years later.

Fourthly, Vanunu is no scientist. He worked at the reactor as a technician. Even if he has a "phenomenal" memory, and even if his blueprints are uncannily exact, it is hard to believe that they have any remaining significance today.

If this is the case, how to explain the renewal of the restrictions? The Attorney General’s representative insisted that their purpose is not to punish him for things he has done in the past, which would be illegal (since he has already been tried and served his full sentence), but to prevent new crimes (the disclosure of further secrets).

I doubt this. One cannot silence Vanunu. The whole world is interested in him, and the more he is persecuted, the more this interest will grow. Vanunu cannot be deterred – he is simple undeterrible (to coin a word). Quite the contrary. Also, it is impossible to prevent him from coming into contact with foreigners. (Some months ago, I was sitting in the evening in the garden of the fabulous American Colony hotel in East Jerusalem, chatting with the British actress Vanessa Redgrave, a tireless campaigner for Israeli-Palestinian peace. Suddenly I noticed Vanunu strolling by. I called him over. Vanessa Redgrave was very interested in his experiences in prison. How can one prevent this sort of things happening?)

There remains only one explanation: Revenge. Yehiel Horev, the chief of the Internal Security Division of the Ministry of Defense, cannot forgive Vanunu for making a mockery of his security arrangements by wandering around the parts of the installation in which he had no business to be, freely taking photos in Israel’s most secret installation and smuggling them abroad. That is indeed infuriating. But vengeance, too, must have its limits.

The more so as the Attorney General’s man, answering a query from Knesset Member Etti Livni, admitted that the same arguments voiced now will also be valid in another year’s time, as well as in five and ten years. In other words, the constraints may be lifelong.

As for my personal opinion about the substance of the matter: Nuclear weapons are a threat to all of us. It is impossible to prevent indefinitely the acquisition of nuclear weapons by more countries in the Middle East – with Iran in the lead. Other categories of Weapons of Mass Destruction (chemical and biological) do already exist in neighboring countries.

For years, Israel has enjoyed a nuclear monopoly in the region. My friends and I have warned that this monopoly is temporary, and that we must use the time to achieve peace. The hubris of our leaders has prevented this.

Now, the aim must be to free the whole region from weapons of mass destruction, under strict international and mutual inspection, as part of a comprehensive peace settlement. That is both possible and practical. When Vanunu rings the bells, he contributes to the public awakening.

His action is also important for another reason: for the first time, he has drawn the attention of the Israeli public to the real danger inherent in the old reactor, which is now more than 40 years old. Several former employees have now sued the government, claiming that they have contracted cancer (and some have died) because of safety failures. What will happen in the case of a Chernobyl-like disaster? Or an earthquake, or a missile strike? Who is thinking about this? Whose responsibility is it? Who oversees those responsible?

Vanunu rings the bells to call attention to a real danger. The question is not whether he is a pleasant person, whether his views are popular or what he thinks about the State of Israel, after 12 years of solitary confinement. The question is whether he is doing a good job.